Argo-cd: Helm repository unsupported protocol scheme "acr"

[gaoshuai2020]

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question in argocd slack channel.

Checklist:

• [x] I've searched in the docs and FAQ for my answer: https://bit.ly/argocd-faq.
• [x] I've included steps to reproduce the bug.
• [x] I've pasted the output of argocd version.

Describe the bug

Seems Argo CD does not support to add helm repository with protocal: "acr".
Does Argo CD only support to add 'http' or 'https' helm repository?

To Reproduce

Try to add a helm repository with protocal "acr". For example: "arc://example.com"

Expected behavior

Helm repository could be added successfully.

Screenshots

Version

argocd: v1.7.1+da5fa74
  BuildDate: 2020-08-26T21:13:01Z
  GitCommit: da5fa74ca1bf9e025dcfe3c8cac083da1b7b45c8
  GitTreeState: clean
  GoVersion: go1.14.1
  Compiler: gc
  Platform: darwin/amd64
argocd-server: v1.7.3+b4c79cc
  BuildDate: 2020-09-01T23:19:02Z
  GitCommit: b4c79ccb88173604c3786dcd34e83a9d7e8919a5
  GitTreeState: clean
  GoVersion: go1.14.1
  Compiler: gc
  Platform: linux/amd64
  Ksonnet Version: v0.13.1
  Kustomize Version: {Version:kustomize/v3.6.1 GitCommit:c97fa946d576eb6ed559f17f2ac43b3b5a8d5dbd BuildDate:2020-05-27T20:47:35Z GoOs:linux GoArch:amd64}
  Helm Version: version.BuildInfo{Version:"v3.2.0", GitCommit:"e11b7ce3b12db2941e90399e874513fbd24bcb71", GitTreeState:"clean", GoVersion:"go1.13.10"}
  Kubectl Version: v1.17.8

Logs

Unable to connect HTTPS repository: Get "acr://xxx/index.yaml": unsupported protocol scheme "acr"

[jessesuen]

In order to support this I think

1. ACR plugin needs to be configured on repo-server like so:
   https://github.com/argoproj/argo-cd/issues/2558#issuecomment-547099146

2. Argo CD needs to support different scheme and fork helm binary to query index.yaml

[jonathanendy]

vote for this also, I'm trying to add helm repo on GCS with the prefix gs://